class Solution
{
    int dx[4] = { 0,0,1,-1 };
    int dy[4] = { 1,-1,0,0 };
    bool check[301][301];

public:
    int numIslands(vector<vector<char>>& grid)
    {

        int ret = 0;
        for (int i = 0; i < grid.size(); i++)
        {
            for (int j = 0; j < grid[0].size(); j++)
            {
                if (grid[i][j] == '1' && check[i][j] == false)
                {
                    ret++;
                    bfs(grid, i, j);
                }
            }
        }
        return ret;
    }
    void bfs(vector<vector<char>>& grid, int i, int j)
    {
        queue<pair<int, int>> q;
        q.push({ i,j });
        check[i][j] = true;
        while (q.size())
        {
            auto [a, b] = q.front();
            q.pop();
            for (int k = 0; k < 4; k++)
            {
                int x = a + dx[k];
                int y = b + dy[k];
                if (x >= 0 && x < grid.size() && y >= 0 && y < grid[0].size() && grid[x][y] == '1' && check[x][y] == false)
                {
                    q.push({ x,y });
                    check[x][y] = true;
                }
            }
        }
    }
};